Synthesis of (2-nitro)alkyl (meth)acrylates has been described in both patent and journal literature (e.g., U.S. Pat. Nos. 2,449,804, 2,388,844 and J. Appl. Polym. Sci. 1968, 12, 1683-1695). Typical procedures involve either (A) direct esterification of (meth)acrylic acid with 2-nitro alcohol in the presence of a mineral or organic acid catalyst in a hydrocarbon solvent that forms an azeotrope with the byproduct water; or (B) esterification reaction of acid chloride of (meth)acrylic acid with 2-nitro alcohol.
Both methods present disadvantages in a commercial scale synthesis of these materials. For example, for direct esterification the strong acid catalyst is removed through some type of wash or ion exchange resin treatment method, thus creating unwanted waste streams. Strong acid catalysts must be removed otherwise they can cause corrosion and can interfere with the applications of the product, for instance in corresponding polymer coatings. In addition, the strong acid catalysts can promote formation of oligomers and alcohol addition products of (meth)acrylic acid that are formed due to Michael addition side reactions. These side reactions often lead to yield loss. Likewise, esterification of acid chlorides requires the disposal of equimolar amounts of chloride salt by-products formed as the result of this chemistry. In addition, acid chloride raw material is not a commercial raw material for commodity applications. Although acid chloride raw material can be manufactured by reacting (meth)acrylic acid with thionyl chloride or phosgene, these reagents are highly toxic and require special handling. This reaction also leads to the formation of more unwanted side products such as sulfur dioxide and hydrochloric acid.
The problem addressed by this invention is the provision of a new process for making (2-nitro)alkyl (meth)acrylates.